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Critical current density and strain effects of Fe/MgB2 tapes with different particle sizes
Université de Genève
Paola Lezza
Co-workers: H. L. SuoV. AbächerliD. UgliettiN. ClaytonC. SenatoreN. MusolinoR. Flükiger
Département de Physique de la Matière Condensée, Université de Genève, 24, quai Ernst Ansermet, 1211 Genève, Switzerland
Université de Genève
Present state of critical current density in MgB2
Tapes preparation
Critical current density Jc for 3 h and 100 h ball milled tapes
n-values
Inductive and transport measurements on 100 h ball milled tape
Irreversibility fields Birr
Strain Effect on 100 h ball milled tape
Conclusion
Outline
Université de Genève
Present state, wires and tapes
Wang
Giunchi
Gümbel
Unige
Dhallé
Goldacker
Wire
Wire
Tape
Bulk
Tape
Bulk
Fe
Fe
Soft S.
Fe
R. Flukiger et al., « Superconducting properties of MgB2 tapes and wires », Physica C 385 (2003) 286-305
Université de Genève
Present state, films
Bu
Kang
Komori
Unige
Film
YSZ
Tape
Film
Film
Al2O3
None
Al2O3
R. Flukiger et al., « Superconducting properties of MgB2 tapes and wires », Physica C 385 (2003) 286-305
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15101
102
103
104
105
106
107
108
Bu Geneva
(tape)//
MgB2
//
20 K4.2 K
Films
0H (T)
J c (A
/cm
2 )
Bu Kang Komori Geneva
(tape)
Université de Genève
Present state, effect of additives
Dou
Zhao
Wang
Unige
Wire
Ti
Y2O3
Tape
Bulk
Bulk
SiC
None
R. Flukiger et al., « Superconducting properties of MgB2 tapes and wires », Physica C 385 (2003) 286-305
0 1 2 3 4 5 6 7 8 9 101112131415100
101
102
103
104
105
106
107
Geneva, without additions
Dou Zhao Wang
Effect of Additives
20 K
4.2 K
MgB2
Dou Zhao Wang
0H (T)J c(
A/c
m2 )
Université de Genève
Preparation
Ball milling under Ar
P. I. T.
Swege
Draw
Flat rolling
in= 5 mm
out= 8 mm
= 3.85 mm
= 2 mm
Tape 4 x 0.38 mm2
P.I.T.
Flat rolling
Final Tape
MgB2
0 1 2 3 4 5 6 7 8 9 101112131415
101
102
103
104
105
100 h ball milling in Ar B tape surface
100 h ball milling in Ar B tape surface
B(T)
J c(A
/cm
2 )
Jc at 4.2 K for different powder grain sizes
Université de Genève
0.1 1 10 60
3 h ball milled
100 h ball milled
100
90
80
70
60
50
40
30
20
10
00 1 2 3 4 5 6 7 8 9 101112131415
101
102
103
104
105
100 h ball milling in Ar
3 h ball milling in Ar
B(T)
J c(A
/cm
2 )
100
90
80
70
60
50
40
30
20
10
0 0.1 1 10 60
4 5 6 7 8 9 10 11 12 13
10
100
3 h ball milling in Ar
100 h ball milling in Ar
B(T)
n-va
lue
n values for Fe/MgB2 tape
Université de Genève
0.1 V/cm
1 V/cm
I
n=148, 4.5 T
n>30, 9.5 T
0.1 V/cm
1 V/cm
I
log-log
Transport measurements on annealed Fe/MgB2 tape 100 h ball milled
Université de Genève
1 2 3 4 5 6 7 8 9 10 11 12 13 14 1510
1
102
103
104
105
30 K20 K 4.2 K
10 K
B(T)
J c(A
/cm
2 )
Irreversibility field as a function of grain size
Université de Genève
Definitions:
R. Flukiger et al., « Superconducting properties of MgB2 tapes and wires », Physica C 385 (2003) 286-305
1) A frequently used definition is based on the resistively measured superconducting transition, the criterion being the 10% of RN or the intersection of the extrapolated linear part of R(T) with R=0
2) The field at which the the inductively measured critical current vanishes
10% RN
R(T)
T
R(T)
T
Jc
B
M
H
Irreversibility field as a function of grain size
Université de Genève
Third Definition:3) The onset of the third harmonic susceptibility, in presence of a magnetic field Hdc>> Hac results from a crossover between a regime in which the system response is flux low dominated (no harmonic signal) and one which is pinnig dominated. The onset of the third harmonic thus corresponds to a non-zero critical current density J c
5 10 15 20 25 30 35 400
2
4
6
8
10
12
14
100 h ball milling
Birr (
T)
T(K)
3 h ball milling
0 2 4 6 8
-0.02
0.00
0.02
0.04
0.06
0.08
3 (S
I u
nits
)
T = 20 KHAC = 8 Oef = 1607 Hz
0H
DC (Tesla)
'3
"3
|3|
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.4005
10152025303540455055606570
9 T
7 T
strain (%)I c
(A)
Strain Effect on MgB2 long tape 100 h ball milled
Université de Genève
Strain gauges
Modified Walters Spiral (WASP)
MgB2 Tape
d=26 cm
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.4005
1015202530354045505560
9 T
7 T
strain (%)
n-va
lue
Université de Genève
Conclusion
The actual state of the critical current densities has been presented, and compared with our latest data.
The critical current densities Jc and the n-values of the Fe/MgB2 tapes, 3 h and 100 h ball milled have been compared. An enhancement is obtained for the smaller particle size.
The critical current densities Jc in the two configurations with the tape surface parallel and perpendicular to the magnetic field direction have been measured. A strong difference has been obtained, reflecting a partial texture of the grains.
The various criteria of the irreversibility field Birr have been discussed.
Strain effects on 100 h ball milled tape have been measured on 80 cm length with a modified Walters Spiral. The degradation of the critical current and the n-values confirming the pre-stress model.
3 4 5 6 7 8 9 10 11 12 13 14 15
10
100
100 h ball milling in ArB tape surface
100 h ball milling in ArB tape surface
B(T)
n-va
lue
n values for Fe/MgB2 tape
Université de Genève